#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>

// 1. 确定主设备号
static int major = 0;
static char kernel_buf[1024];

static struct class *hello_class;

#define MIN(a, b) (a < b ? a : b)

// 3. 实现对应的open/read/write等函数，填入 file_operations 结构体
static ssize_t hello_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset) {
    int err;
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    err = copy_to_user(buf, kernel_buf, MIN(1024, size));
    return MIN(1024, size);
}

static ssize_t hello_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset) {
    int err;
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    err = copy_from_user(kernel_buf, buf, MIN(1024, size));
    return MIN(1024, size);
}

static int hello_drv_open (struct inode *node, struct file *file) {
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    return 0;
}

static int hello_drv_close (struct inode *node, struct file *file) {
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    return 0;
}

// 2. 定义自己的 file_operations 结构体
static struct file_operations hello_drv = {
    .owner	 = THIS_MODULE,
    .open    = hello_drv_open,
    .read    = hello_drv_read,
    .write   = hello_drv_write,
    .release = hello_drv_close,
};

// 4. 把 file_operations 结构体告诉内核： 注册驱动程序
// 5. 谁来注册驱动程序啊？得有一个入口函数：安装驱动程序时，就回去调用这个入口函数
static int __init hello_init(void) {
    int err;
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    major = register_chrdev(0, "hello", &hello_drv);    /* /dev/hello */

    hello_class = class_create(THIS_MODULE, "hello_class");
    err = PTR_ERR(hello_class);
	if (IS_ERR(hello_class)) {
        printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
        unregister_chrdev(major, "hello");
        return -1;
    }

    device_create(hello_class, NULL, MKDEV(major, 0), NULL, "hello");   /* /dev/hello */

    return 0;
}

// 6. 有入口函数就应该有出口函数：卸载驱动程序时，就回去调用这个出口函数
static void __exit hello_exit(void) {
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    device_destory(hello_class, MKDEV(major, 0));
    class_destory(hello_class);

    unregister_chrdev(major, "hello");
}

// 7. 其他完善：提供设备信息，自动创建设备节点
module_init(hello_init);
module_exit(hello_exit);

MODULE_LICENSE("GPL");